1, Field of the Invention
The present invention relates to a double rotation type scroll expander in which a drive scroll body integrated with a drive shaft and a driven scroll body rotate synchronously.
2, Description of the Related Art
Conventional power generation systems tend mostly to be large scale plants generating at least several hundred kW, while small scale power generation is performed mostly by simply structured engine power generators and the like. Recently, however, due to increased awareness of the need for energy conservation, passage of the Act on Special Measures Concerning Procurement of Renewable Electric Energy by Operators of Electric Utilities, and the like, a need and a market for small scale power generation are gradually increasing. Photovoltaic generation and wind force power generation, on the other hand, have not yet improved in cost-effectiveness. Meanwhile, a binary power generation system that uses hot water or steam at 75 to 150° C. as a heat source to drive a small scale power generator via a working medium having a low boiling point has been developed.
Amid these developments, a scroll expander, which exhibits little torque variation, has come to attract of attention as a favorable expander for use in a small scale power generation system. In a scroll type fluid machine, a compression chamber and an expansion chamber are formed in a crescent shape by end plates and spiral-shaped wraps of a pair of scroll bodies. Japanese Patent Application Publication No. 2009-299653 discloses a one-side revolving type scroll expander in which one of the pair of scroll bodies is a fixed scroll body and the other is a revolving scroll body, and the expansion chamber is formed by causing the revolving scroll body to revolve relative to the fixed scroll body. A scroll type fluid machine thus configured is dynamically sealed, and therefore noise and wear tend to increase in contact sites with the end plates and the wraps forming the expansion chamber, whereby a sealing property of the expansion chamber may be impaired.
Japanese Patent Application Publication No. H6-341381 discloses a double rotation type scroll fluid machine. In a double rotation type scroll fluid machine, a drive scroll body and a driven scroll body are rotated synchronously via an interlocking mechanism, and therefore noise and wear in the contact sites can be reduced. In the double rotation type scroll fluid machine, the compression chamber and the expansion chamber are formed by causing the driven scroll body to rotate eccentrically relative to the drive scroll body.
The double rotation type scroll fluid machine disclosed in Japanese Patent Application Publication No. H6-341381 has a so-called “double wrap scroll structure” in which the compression chamber or the expansion chamber is formed on both surface sides of an end plate of the driven scroll body. By forming the compression chamber or the expansion chamber on both sides in this manner, a high-pressure fluid supply amount and an output (a rotary torque) can be increased. Further, a thrust direction load exerted on the drive scroll body and the driven scroll body can be canceled out, and therefore a support structure for the drive scroll body and the driven scroll body can be simplified.
Japanese Patent Application Publication No. S59-34494 discloses a configuration of a scroll type fluid machine having a fixed scroll body and a revolving scroll body in which an adiabatic material is buried in the end plate of the revolving scroll body. In so doing, heat transfer from the compression chamber and the expansion chamber to a bearing that supports a drive shaft of the revolving scroll body can be prevented. Japanese Patent Application Publication No. 2004-286025 discloses a configuration in which a fan blade is formed on the endplate of the drive scroll body, and an interior of a housing is cooled by introducing cooling air into the housing from the outside using the fan blade.
In a scroll expander, the drive shaft is rotated by an expansion force of a high-temperature, high-pressure working medium supplied to the expansion chamber. Therefore, when a leak of the working medium or pre-expansion due to a temperature reduction in the working medium occurs before the working medium is supplied to the expansion chamber, the output (the rotary torque) of the drive shaft decreases. To obtain a high output, therefore, it is necessary to prevent pre-expansion by improving a sealing property of a supply passage that supplies the working medium to the expansion chamber. In the case of a double rotation type scroll expander, however, the drive scroll body and the driven scroll body rotate in conjunction with each other, and it is therefore not easy to secure a working medium supply passage. With a scroll expander having a double wrap scroll structure in particular, the working medium must be introduced into double expansion chambers, making it even more difficult to secure a supply passage.
When the scroll compressor disclosed in Japanese Patent Application Publication No. H6-341381 is used as an expander, the high-temperature, high-pressure working medium is supplied to the expansion chamber through an introduction hole provided in the drive shaft. With this supply method, however, a bearing that supports the drive shaft and the driven scroll body rotatably may deteriorate due to exposure to the heat of the working medium, whereby the lifespan of the bearing and grease sealed inside the bearing may decrease.